Question 1

Which of the following statements best explains why carbon is considered the backbone of biological molecules?

Accepted Answer

Carbon can form up to four covalent bonds, allowing for a diversity of stable molecular structures.

Question 2

A neutral atom of oxygen has an atomic number of 8 and an atomic mass of 16. How many neutrons does it contain?

Accepted Answer

$$16 - 8 = 8$$ neutrons

Question 3

Which of the following best describes an isotope?

Accepted Answer

Atoms of the same element with different numbers of neutrons

Question 4

Which type of chemical bond is primarily responsible for the unique properties of water, such as its high surface tension and boiling point?

Accepted Answer

Hydrogen bonds

Question 5

A sodium atom (Na) has 11 protons and 11 electrons. When it forms an ion, it loses one electron. What is the resulting charge and why?

Accepted Answer

The ion has a $$+1$$ charge because it has one more proton than electron.

Question 6

Which of the following elements is NOT one of the six most abundant elements in living organisms (CHNOPS)?

Accepted Answer

Calcium (Ca)

Question 7

What is the maximum number of electrons that can occupy the second energy shell of an atom?

Accepted Answer

$$8$$ electrons

Question 8

Which of the following best describes a polar covalent bond?

Accepted Answer

A bond in which electrons are shared unequally between two atoms

Question 9

A radioactive isotope of carbon, $$^{14}C$$, is used in dating fossils. What makes $$^{14}C$$ radioactive?

Accepted Answer

It has an unstable nucleus that emits particles and energy.

Question 10

Which of the following is a correct calculation for the number of neutrons in a nitrogen atom with atomic number 7 and atomic mass 14?

Accepted Answer

$$14 - 7 = 7$$ neutrons

Question 11

Which statement best explains why trace elements like iron (Fe) are essential for life?

Accepted Answer

They are required in minute quantities for proper biological function, such as oxygen transport.

Question 12

Which of the following best describes the octet rule?

Accepted Answer

Atoms tend to complete their valence shell with 8 electrons.

Question 13

Which of the following molecules is an example of a diatomic molecule?

Accepted Answer

$$O_2$$

Question 14

If an atom has 6 protons, 6 neutrons, and 6 electrons, what is its atomic mass?

Accepted Answer

$$6 + 6 = 12$$

Question 15

Which of the following best describes a cation?

Accepted Answer

A positively charged ion formed by losing electrons

Question 16

Which property of water is most directly a result of hydrogen bonding?

Accepted Answer

High surface tension

Question 17

Which of the following best explains why sodium chloride (NaCl) forms an ionic bond?

Accepted Answer

Sodium donates an electron to chlorine, resulting in oppositely charged ions that attract each other.

Question 18

Which of the following is true about the location and charge of subatomic particles in an atom?

Accepted Answer

Protons and neutrons are in the nucleus; electrons orbit the nucleus.

Question 19

Which of the following best describes the difference between a polar and a non-polar covalent bond?

Accepted Answer

Polar covalent bonds involve unequal sharing of electrons, while non-polar covalent bonds involve equal sharing.

Question 20

A patient is injected with a radioactive isotope for a PET scan. Which property of the isotope is most important for this medical application?

Accepted Answer

It emits detectable particles and energy as it decays.

The Chemical Components of Cells: Atoms, Elements, and Bonding

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